Sign up to receive free email alerts when patent applications with chosen keywords are publishedSIGN UP

Abstract:

An apparatus and method for quiescently filling of a ladle with molten
material and transferring of the molten material from the ladle is
disclosed, wherein the molten material is transferred from the ladle to a
casting mold to minimize turbulence in the molten material to minimize
defects in a desired cast object.

Claims:

1. A casting apparatus comprising:a ladle having a hollow interior adapted
to receive a molten material therein, wherein said ladle is adapted to
pivot about an eccentric axis; anda mold having a cavity formed therein
adapted to receive the molten material, wherein said ladle abuts said
mold, and said mold and said ladle are cooperatively rotated to pour the
molten material from said ladle into the cavity of said mold.

2. The casting apparatus of claim 1, wherein a pin is formed on side walls
of said ladle to facilitate pivoting thereof.

3. The casting apparatus of claim 1, wherein an aperture is formed in said
ladle to facilitate a pouring of the molten material therefrom.

4. The casting apparatus of claim 3, wherein the aperture has a length
substantially equal to a length of the cavity of said mold.

5. The casting apparatus of claim 1, wherein pivoting of said ladle about
the eccentric axis minimizes turbulent flow of the molten material
introduced therein.

6. The casting apparatus of claim 1, wherein a drop of the molten material
from said ladle into the cavity of said mold is minimized to militate
against turbulence.

7. The casting apparatus of claim 1, wherein said ladle and said mold are
integrally formed.

8. The casting apparatus of claim 1, wherein said ladle and said mold are
separately formed and coupled together.

9. A casting apparatus comprising:a ladle having a hollow interior adapted
to receive a molten material therein, said ladle having an aperture
formed therein, wherein said ladle is adapted to pivot about an eccentric
axis; anda mold having a cavity formed therein adapted to receive the
molten material, wherein said ladle abuts said mold, and said mold and
said ladle are cooperatively rotated to pour the molten material from
said ladle into the cavity of said mold.

10. The casting apparatus of claim 9, wherein a pin is formed on side
walls of said ladle to facilitate pivoting thereof.

11. The casting apparatus of claim 9, wherein an aperture is formed in
said ladle to facilitate a pouring of the molten material therefrom.

12. The casting apparatus of claim 11, wherein the aperture has a length
substantially equal to a length of the cavity of said mold.

13. The casting apparatus of claim 9, wherein pivoting of said ladle about
the eccentric axis minimizes turbulent flow of the molten material
introduced therein.

14. The casting apparatus of claim 9, wherein a drop of the molten
material from said ladle into the cavity of said mold is minimized to
militate against turbulence.

15. The casting apparatus of claim 9, wherein said ladle and said mold are
integrally formed.

16. The casting apparatus of claim 9, wherein said ladle and said mold are
separately formed and coupled together.

17. A method of transferring a molten material to a casting mold, the
method comprising:providing a ladle having a hollow interior adapted to
receive a molten material therein, the ladle having an aperture formed
therein, wherein the ladle is adapted to rotate about an eccentric
axis;providing a mold having a cavity formed therein adapted to receive
the molten material, wherein the ladle abuts the mold and the mold and
the ladle are cooperatively rotated to pour the molten material from the
ladle into the cavity of the mold;filling the ladle with the molten
material;positioning the aperture of the ladle adjacent the cavity of the
mold; androtating the mold and ladle to facilitate the pouring of the
molten material from the ladle into the cavity of the mold.

18. The method of claim 17, wherein said ladle and said mold are
integrally formed.

19. The method of claim 18, wherein said ladle is filled with the molten
material by causing the molten material to flow from a furnace through a
nozzle.

20. The method of claim 17, wherein said ladle and said mold are
separately formed and coupled together.

Description:

FIELD OF THE INVENTION

[0001]This invention relates to an apparatus and method for the
quiescent-fill of a ladle and the transfer of a molten material from the
ladle to a casting mold to minimize turbulence in the molten material to
minimize defects in a desired cast object formed by a tilt pour molding
process.

BACKGROUND OF THE INVENTION

[0002]The pouring of a molten material, such as metal, for example, into a
casting mold is a significant process variable that influences the
internal soundness, surface conditions, and mechanical properties, such
as tensile strength, porosity, percent elongation and hardness, of a cast
object. Many different designs for dipping/pouring ladles exist and are
used in the foundry industry. The designs are normally chosen based upon
the type of molten material and casting mold used. Commonly used ladles
make use of a slot, a lip and a baffle, or a dam at the top of the ladle
to reduce inclusion of furnace metal oxides during metal filling, or the
ladle may incorporate a stopper rod to control the flow of metal into and
out of the ladle.

[0003]Molten metals, such as aluminum, for example, react with the air and
create oxides, commonly known as dross, which upon mixing with the rest
of the molten metal creates inclusions and highly porous regions in the
cast object during solidification of the metal. While many factors
influence and account for undesirable properties in the cast object, two
common sources of inclusions include formation of a dross layer on top of
the molten metal, and the folding action of the molten metal caused by
turbulent flow of the molten metal during pouring. Turbulent metal flow
exposes the molten metal surface area to the air which creates the dross
layer. Depending on the velocity of the molten metal, dictated by the
pouring ladle and basin design and use, the molten metal may fold-over
itself many times, thereby trapping oxygen and metal oxide layers therein
and exposing additional surface area of the metal to the air.

[0004]Typical foundry ladles are referred to as teapot-type ladles. These
ladles are substantially cylindrical in shape with an external spout
extending outwardly from the top thereof. Certain teapot ladles have
incorporated a wall or a baffle to separate the bowl or cavity area of
the ladle from the spout. The wall or baffle may extend to the bottom of
the ladle. When the molten metal is poured, the baffle restricts the flow
of molten metal from the top of the ladle to facilitate the pouring of
the metal that is near the bottom of the ladle. The metal at the bottom
of the ladle is substantially free from dross and other foreign material
that may be present, such as eroded refractory lining and ash created
during a melting process of the metal. Although the baffle serves to
minimize dross inclusion, the external spout design still increases the
velocity of the material upon pouring, and may create turbulent flow.
Next, the molten metal is typically transferred from the ladle to a
casting mold through a pour basin. In traditional pour basin designs,
molten material flows down the basin to a mold sprue. The flow of the
molten metal through the sprue may also cause turbulence therein, thereby
creating additional dross.

[0005]Low pressure, bottom pour furnaces have been known to produce
castings with minimized dross, but the equipment is expensive, complex,
and subject to high maintenance requirements. In addition, the bottom
pour furnaces increase capital costs. Hot Isostatic Pressing (HIPping) of
castings may also reduce porosity in aluminum castings, however HIPping
is expensive and may cause dimensional changes to the casting that may
not be uniform or replicable.

[0006]Thus, there remains a need for an economical method and apparatus
that would prevent or minimize the inclusion of dross and contaminants
leading to high porosity and/or low mechanical properties of cast
materials.

[0007]It would be desirable to provide an apparatus and method for the
quiescent-fill of a ladle and the transfer of a molten material from the
ladle to a casting mold to minimize turbulence in the molten material to
minimize defects in the desired cast object formed by a tilt pour molding
process.

SUMMARY OF THE INVENTION

[0008]Concordant and congruous with the present invention, an apparatus
and method for the quiescent-fill of a ladle and the transfer of a molten
material from the ladle to a casting mold to minimize turbulence in the
molten material to minimize defects in the desired cast object formed by
a tilt pour molding process, have surprisingly been discovered.

[0009]In one embodiment, a casting apparatus comprises a ladle having a
hollow interior adapted to receive a molten material therein, wherein
said ladle is adapted to pivot about an eccentric axis; and a mold having
a cavity formed therein adapted to receive the molten material, wherein
said ladle abuts said mold, and said mold and said ladle are
cooperatively rotated to pour the molten material from said ladle into
the cavity of said mold.

[0010]In another embodiment, a casting apparatus comprises a ladle having
a hollow interior adapted to receive a molten material therein, said
ladle having an aperture formed therein, wherein said ladle is adapted to
pivot about an eccentric axis; and a mold having a cavity formed therein
adapted to receive the molten material, wherein said ladle abuts said
mold, and said mold and said ladle are cooperatively rotated to pour the
molten material from said ladle into the cavity of said mold.

[0011]In another embodiment, a method of transferring a molten material to
a casting mold, the method comprises providing a ladle having a hollow
interior adapted to receive a molten material therein, the ladle having
an aperture formed therein, wherein the ladle is adapted to rotate about
an eccentric axis; providing a mold having a cavity formed therein
adapted to receive the molten material, wherein the ladle abuts the mold
and the mold and the ladle are cooperatively rotated to pour the molten
material from the ladle into the cavity of the mold; filling the ladle
with the molten material; positioning the aperture of the ladle adjacent
the cavity of the mold; and rotating the mold and ladle to facilitate the
pouring of the molten material from the ladle into the cavity of the
mold.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]The above, as well as other advantages of the present invention,
will become readily apparent to those skilled in the art from the
following detailed description of a preferred embodiment when considered
in the light of the accompanying drawings in which:

[0013]FIG. 1 is a perspective view of a molding apparatus including a
ladle and a mold rotated ninety degrees according to an embodiment of the
invention;

[0014]FIG. 2 is a perspective view of the ladle of FIG. 1; and

[0015]FIG. 3 is a perspective view of a molding apparatus including a
ladle and a mold rotated ninety degrees according to another embodiment
of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016]The following detailed description and appended drawings describe
and illustrate various exemplary embodiments of the invention. The
description and drawings serve to enable one skilled in the art to make
and use the invention, and are not intended to limit the scope of the
invention in any manner. In respect of the methods disclosed, the steps
presented are exemplary in nature, and thus, the order of the steps is
not necessary or critical.

[0017]FIG. 1 shows a casting apparatus 10 according to an embodiment of
the invention. The casting apparatus 10 includes ladle 12 adapted to
receive a molten material 16 therein and to pour the molten material 16
therefrom. A mold 14 is provided in fluid communication with the ladle 12
and is adapted to receive the molten material 16 therefrom. It is
understood that the molten material 16 may be any molten material such as
a metal or a polymer, for example, as desired.

[0018]The ladle 12 is a quiescent-fill ladle similar to the ladle
disclosed in commonly owned U.S. Pat. No. 7,025,115, hereby incorporated
herein by reference in its entirety. As used herein, the term
"quiescent-fill" is defined as a ladle adapted to receive a molten
material therein with a minimized amount of turbulence, agitation, and
folding of the molten material. The ladle 12 may be formed from any
conventional material such as a ceramic or a metal, for example, as
desired. In the embodiment shown in FIGS. 1 and 2, the ladle 12 includes
a hollow interior 26. The ladle 12 is formed by a pair of planar side
walls 18, a substantially planar front wall 28, and a curvilinear wall
30. The side walls 18 are each defined by a curvilinear edge 20, a first
rectilinear edge 22, and a second rectilinear edge 24. The second
rectilinear edge 24 is adapted to abut the mold 14. Each side wall 18
includes an pin 32 formed thereon. In the embodiment shown, the pins 32
are adapted to facilitate a pivoting of the ladle 12 about an eccentric
axis of rotation of the ladle 12 such that the front wall 28 pivots
downwardly when the ladle 12 is filled with a molten material. It is
understood that the pins 32 may be formed with the side walls 18, or the
pins 32 may be separately formed and attached to the side walls 18.

[0019]The front wall 28 of the ladle 12 is adapted to substantially abut
the mold 14. A second aperture 34 is formed in the front wall 28 of the
ladle 12. In the embodiment shown, the second aperture 34 has a length
substantially equal to a length of the front wall 28. However, the second
aperture 34 may have any length, as desired. A top of the front wall 28
of the ladle 12 may include a protuberant portion or lip. The protuberant
portion may be formed on an exterior of the front wall 28 or the interior
of front wall 28 of the ladle 12, as desired. The curvilinear wall 30
forms a bottom wall and a back wall of the ladle 12. However, the bottom
wall and back wall of the ladle 12 may be formed from a combination of a
substantially planar wall and a curvilinear wall, a pair of substantially
planar walls, or a pair of curvilinear walls, as desired.

[0020]In the embodiment shown in FIG. 1, the mold 14 is adapted to receive
a molten material therein through a tilt-pour process. The mold 14
includes a body portion 36 forming a cavity 38 therein. A length of the
cavity 38 is substantially equal to the length of the second aperture 34
formed in the front wall 28 of the ladle 12. The cavity 38 of the mold 14
may have the shape of any desired cast object, such as an engine block, a
cylinder head, a complex transmission component, and the like, for
example. The mold 14 also includes risers 40 adapted to form reservoirs
that militate against the formation of cavities or voids in the desired
cast object due to shrinkage of the molten material 16 during a cooling
and solidification thereof.

[0021]In use, the ladle 12 is filled with the molten material 16 during a
filling operation which includes: (1) positioning the ladle 12 in a rest
position over a furnace dip well or crucible (not shown) filled with the
molten material 16; (2) lowering the ladle 12 to the surface of the
molten material 16 and making initial contact between the ladle 12 and
the molten material 16; (3) rotating the ladle 12 about the eccentric
axis on the pins 32 and exposing a portion of the aperture 34 to the
molten material 16, thereby minimizing the drop of the molten material 16
into the ladle 12 during filling; (4) lowering the ladle 12 to a desired
depth into the crucible; (5) rotating the ladle 12 back to the rest
position; and (6) raising the ladle 12 containing molten material 16 from
the crucible. By minimizing the drop of the molten material 16 into the
ladle 12, turbulent flow of the molten material 16 into the ladle 12 and
the folding of the molten material 16 therein is minimized.

[0022]As shown in FIG. 1, the mold 14 is rotated ninety degrees in respect
of a floor or a surface parallel to the floor with a top of the cavity 38
thereof substantially perpendicular to the front wall 28 of the ladle 12.
The second aperture 34 of the ladle 12 is positioned adjacent the cavity
38, with the front wall 28 of the ladle 12 abutting the mold 14. It is
understood that the ladle 12 may be positioned adjacent to the cavity 38
with a small gap between the front wall 28 and the mold 14. The ladle 12
and the adjacent mold 14 are then rotated or otherwise controlled in
unison, either secured together with attaching means (not shown) or by
synchronized control of the ladle 12 and mold 14 together. The casting
apparatus 10, which includes the ladle 12 and mold 14, is then caused to
rotate ninety degrees as indicated by the arrow R about the eccentric
axis on the pins 32 which may be located at a junction of the ladle 12
and the mold 14 or at the base of the mold 14, as desired. The rate of
rotation of the casting apparatus 10 is regulated to facilitate a
gravity-assisted, low velocity pour of the molten material 16 into the
cavity 38 of the mold 14. Since the molten material 16 is poured directly
into the cavity 38 and not into a gate system, the drop of the molten
material 16 from the ladle 12 and into the cavity 38 is minimized. Since
turbulence and folding of the molten material 16 are minimized,
entrapment of air in the molten material 16 and oxidation of the molten
material 16 are minimized, thereby minimizing deformities and defects and
maximizing the quality of the cast object.

[0023]Once the molten material 16 has been allowed to cool and harden, the
three-dimensional cast object may be removed from the mold 14. The cast
object may then be further machined to result in a final shape thereof.
Additional heat treating operations, coating processes, and the like can
also be conducted on the casting.

[0024]FIG. 3 shows a casting apparatus 10' according to another embodiment
of the invention similar to the molding apparatus 10 of FIGS. 1 and 2
except as described below. This embodiment of FIG. 3 facilitates a ladle
12 width that does not cover the entire width of the cavity 38 of the
mold 14. Having a ladle 12 with a width less than the width of the cavity
38 is desired when the cavity 38 of the mold 14 is so wide that a ladle
having a matching width would be cumbersome to handle and difficult to
fill with a dipping well or crucible. This embodiment allows for a
reduced ladle width without the risk of spilling metal out of the open
mold areas. Like structure from FIGS. 1 and 2 repeated in FIG. 3 includes
identical reference numerals accompanied by a prime (') symbol.

[0025]The casting apparatus 10' includes a ladle 12' adapted to receive
and pour a molten material 16'. A mold 14' is adapted to receive the
molten material 16' from the ladle 12'. It is understood that the molten
material 16' may be any molten material such as a metal or a polymer, for
example, as desired.

[0026]The ladle 12' may be formed from any conventional material such as a
ceramic or a metal, for example, as desired. In the embodiment shown, the
ladle 12' includes a hollow interior 26' formed by a pair of planar side
walls 18', a substantially planar front wall 28', and a curvilinear wall
30'. The side walls 18' are each defined by a curvilinear edge 20', a
first rectilinear edge 22', and a second rectilinear edge 24'. The second
rectilinear edge 24' is adapted to abut the mold 14'. Each side wall 18'
includes a pin 32' formed thereon. In the embodiment shown, the pins 32'
are adapted to facilitate the rotation of the ladle 12' on the pins 32'
about an eccentric axis of rotation of the ladle 12'. It is understood
that the pins 32' may be formed with the side walls 18', or the pins 32'
may be separately formed and attached to the side walls 18'. However, the
bottom wall and back wall of the ladle 12' may be formed from a
combination of a rectilinear wall and a curvilinear wall, a pair of
rectilinear walls, or a pair of curvilinear walls, as desired.

[0027]The front wall 28' of the ladle 12' is adapted to substantially abut
the mold 14'. A second aperture 34' is formed in the front wall 28' of
the ladle 12'. In the embodiment shown, the second aperture 34' has a
length substantially equal to a length of the front wall 28', but the
second aperture 34' may have any length, as desired. A top of the front
wall 28' of the ladle 12' may include a protuberant portion or lip. The
protuberant portion may be formed on an exterior of the front wall 28' or
the interior of front wall 28' of the ladle 12', as desired. The
curvilinear wall 30' defines a bottom wall and a back wall of the ladle
12'.

[0028]In the embodiment shown in FIG. 3, the mold 14' is adapted to
receive a molten material therein through a tilt-pour process. The mold
14' includes a body portion 36' forming a cavity 38' therein and a pair
of mold features 42 adapted to militate against a spilling of the molten
material 16' from the mold cavity 38' during the tilt-pour process. A
length of the cavity 38' is longer than the length of the second aperture
34' formed in the front wall 28' of the ladle 12'. The cavity 38' of the
mold 14' may have the shape of any desired cast object, such as an engine
block, a cylinder head, a complex transmission component, and the like,
for example. The mold features 42 are disposed adjacent to the side walls
18' of the ladle 12' when the ladle 12' is disposed adjacent to the mold
14'. The mold features have a height greater than the height of the
portion of the mold cavity 38' disposed adjacent to the ladle 12'. The
dimensions of the mold features 42 will vary based on the design of the
ladle 12' and the rate at which the ladle 12' and the mold 14' are
rotated during the tilt-pour process. As the rate of rotation increases,
the rate of pouring of the molten material 16' increases, thereby
increasing the height of the molten material 16' in the mold cavity 38'
to a height above the aperture 34' of the ladle 12'. As the height of the
molten material 16' in the mold cavity 38' increases, the dimensions of
the mold features 42 increase to militate against spilling. The mold 14'
also includes risers 40' adapted to form reservoirs that militate against
the formation of cavities or voids in the desired cast object due to
shrinkage of the molten material 16' during a cooling and solidification
thereof.

[0029]In use, the ladle 12' is filled with the molten material 16 during a
filling operation which includes: (1) positioning the ladle 12' in a rest
position over a furnace dip well or crucible (not shown) filled with the
molten material 16'; (2) lowering the ladle 12' to the surface of the
molten material 16' and making initial contact between the ladle 12' and
the molten material 16'; (3) rotating the ladle 12' about the eccentric
axis on the pins 32' and exposing a portion of the aperture 34' to the
molten material 16', thereby minimizing the drop of the molten material
16' into the ladle 12' during filling; (4) lowering the ladle 12' to a
desired depth into the crucible; (5) rotating the ladle 12' back to the
rest position; and (6) raising the ladle 12' containing molten material
16' from the crucible. By minimizing the drop of the molten material 16'
into the ladle 12', turbulent flow of the molten material 16' into the
ladle 12' and the folding of the molten material 16' therein is
minimized.

[0030]As shown in FIG. 3, the mold 14' is rotated ninety degrees in
respect of the floor or a surface parallel to the floor with a top of the
cavity 38' substantially perpendicular to the ladle 12'. The second
aperture 34' of the ladle 12' is positioned adjacent the cavity 38', with
the front wall 28' of the ladle 12' abutting the mold 14'. It is
understood that the ladle 12' may be positioned adjacent to the cavity
38' with a small gap between the front wall 28' and the mold 14'. The
ladle 12' and the adjacent mold 14' are then rotated or otherwise
controlled in unison, either secured together with attaching means (not
shown) or by synchronized control of the ladle 12' and mold 14' together.
The casting apparatus 10', which includes the ladle 12' and mold 14', is
then caused to rotate ninety degrees as indicated by the arrow R' about
the eccentric axis on the pins 32' which may be located at a junction of
the ladle 12' and the mold 14' or at the base of the mold 14', as
desired. The rate of rotation of the casting apparatus 10' is regulated
to facilitate a gravity-assisted, low velocity pour of the molten
material 16' into the cavity 38' of the mold 14'. As the molten material
16' enters the cavity 38', the molten material 16' flows therethrough
filling void space in the cavity 38' until filled to a desired level.
Since the molten material 16' is poured directly into the cavity 38' and
not into a gate system, the drop of the molten material 16' from the
ladle 12' and into the cavity 38' is minimized, thereby minimizing the
turbulent flow and the folding thereof. Since turbulence and folding of
the molten material 16' are minimized, entrapment of air in the molten
material 16' and oxidation of the molten material 16' are minimized,
thereby minimizing the deformities and maximizing the quality of the cast
object.

[0031]Once the molten material 16' has been allowed to cool and harden,
the three-dimensional cast object may be removed from the mold 14'. The
cast object may then be further machined to result in a final shape
thereof. Additional heat treating operations, coating processes, and the
like can also be conducted on the casting.

[0032]The foregoing discussion discloses and describes merely exemplary
embodiments of the present invention. One skilled in the art will readily
recognize from such discussion and from the accompanying drawings and
claims that various changes, modifications and variations can be made
therein without departing from the spirit and scope of the invention as
defined in the following claims.